Sauerstoffspeicher für die oxidkeramische Batterie:  Herstellung, Charakterisierung und Betriebsverhalten

Berger, Cornelius M.

Dissertation / PhD Thesis

FZJ-2016-03391

Sauerstoffspeicher für die oxidkeramische Batterie: Herstellung, Charakterisierung und Betriebsverhalten

Berger, C. M. (Corresponding author)FZJ*

2016
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-154-5

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich Reihe Energie & Umwelt / Energy & Environment 326, XV, 130 S. (2016) = Universität Bochum, Diss., 2016

Please use a persistent id in citations: http://hdl.handle.net/2128/12301

Abstract: A Rechargeable Oxide Battery (ROB) comprises high temperature regenerative solid oxide cells (rSOC) as energy converters and a porous metal/metal-oxide as storage material for oxygen ions. The rSOCs work in turns in fuel cell- and electrolyzer mode at approximately 800°C. Instead of externally storing the fuel, a stagnant atmosphere consisting of hydrogen and steam is used directly as an oxidizing and reducing agent for the iron base storage material which is located inside the rSOC stack close to the fuel electrode. As a consequence, all the expenses related to pumping losses, heat losses and further components can be avoided, compared to the conventional rSOC system with external storage. Using iron as economic, ecologic, and only feasible storage material results in a maximal theoretical storage capacity of up to 1600 Wh/kg storage. However, the capacity of the battery fades with an increasing number of charge-discharge cycles. Therefore, the scientific challenges in this work are to understand and prevent degradation of the storage medium which is near net-shaped via powder technology. Degradation mainly mainfests as particle coarsening (sintering) and layer formation on top of the porous storage medium. These phenomena entail a decreased active surface and a deteriorated exchange velocity of gas. This work focuses on the effect of the chemical composition and the microstructure on the degradation of the storage components. To mitigate degradation, iron is mixed with stabilising oxides such as calcia (CaO) or zirconia (ZrO$_{2}$). Also, different manufacturing routes and resulting microstructures are evaluated as to whether the degradation properties improve. For accelerated degradation testing, storage components are ex-situ exposed in an environmental furnace to conditions that simulate those present in the battery. Likewise, the electrochemical performance and the long-term stability of the rSOCs are characterized in-situ in battery tests. More than 200 cycles were achieved during battery testing with power densities of 130-170 mW/cm$^{2}$ and durations of more than 60 min/cycle. Microstructural analysis showed that addition of the oxides to the iron base results in a mitigation of degradation effects. Thermogravimetric studies, scanning electron microscopy and Mössbauer spectrometry show a very different mechanism if CaO is used as a scaffold instead of ZrO$_{2}$. While the latter is inert towards iron under battery conditions and acts as a mere spacer between the iron particles, calcia reacts with iron forming a number of mixed oxides depending on the exact partial pressure of oxygen. The reversible formation of mixed oxid phases between iron oxide and calcia leads to a more sustained scaffolding function as compared to when inert ZrO$_{2}$ is used.

Note: Universität Bochum, Diss., 2016

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